Detailed studies on the interaction of anticancer drugs and X-rays in both murine model systems and human tumor isolates are in progress. Of particular interest are the drugs capable of blocking repair replication and the rejoining of single strand breaks. Common to these agents is their ability to bind strongly to cellular DNA. Radiosensitization has been demonstrated for Adriamycin using squamous cell lines derived from malignant cervical epidermoid cancers which appear to lack repair replication enzymes.